The coordinates of points in the graph are,
[tex](-4,-1), (-2,1), (0,-3), (2,3)[/tex]
and
[tex](4,-2)[/tex]
Any other point whose first coordinate(the x-co-ordinate) coincides with one of these points will make the relation not a function.
The relation becomes one- to-many relation which is not a function.
It will also fail the vertical line test , if the points are connected with line segments.
One of such point is,
[tex](4,3)[/tex]